The conventional techniques for manufacturing high-voltage or power devices in HVICs or PICs are Dielectric Isolation (DI), p-n Junction Isolation (JI) and Self Isolation (SI). Among these three techniques, the isolation performance of DI is the best, and the isolation performance of the JI is better than that of SI, whereas the cost of SI is the lowest, and the cost of DI is the highest. The technique of reduced surface field (RESURF) is often used in SI, and the breakdown voltage by using such method is normally only 70% of that of a parallel plane junction made by the same substrate. Furthermore, the specific on-resistance Ron of the devices by using the technique of RESURF is high. For references of those techniques one can see Ref [1].
As shown in FIG. 1, a conventional HVIC, 100, includes four portions: a low-voltage control circuit 101, a low-side driver 102, a high-voltage level shifter 103, and a high-side driver 104. It can be seen that the low-side driver 102 is connected to the input terminal of low-side n-type Metal-Oxide-Semiconductor Transistor (n-MOST) 105, and the high-side driver 104, is connected to the input terminal of a high-side n-MOST 106. Here, a common terminal of the high-side driver 104 is connected with an output terminal of a totem pole connection point of two devices. The connection point of these two devices is called TUB, whose voltage with regard to the ground can vary from the voltage of the ground, i.e. zero up to that of a high bus-voltage. That is to say, the TUB has a floating voltage terminal. Both of the low-side driver 102 and the low-voltage control circuit 101 are low-voltage circuits, and the power supply for them uses the ground as a reference, whereas the high-side driver 104 is a low-voltage circuit using the voltage of the floating terminal of the TUB as a reference. The output terminal of the low-voltage control circuit, 101, is used as the input terminal of the high-voltage level shifter 103 in FIG. 1. The output terminal of the high-voltage level shifter 103 is used as the input terminal of the high-side driver, 104, with a voltage varying from that of ground up to the highest voltage, therefore, the high-voltage level shifter 103 must have high voltage devices therein.
In Ref [2-4], the present inventor proposes some techniques to implement high-side and low-side devices which can bear high voltage by taking advantage of optimum variation lateral doping. The techniques are CMOS and/or Bi-CMOS technology-compatible without using DI and JI techniques for manufacturing devices, so that high-side and low-side devices as well as a low-voltage high-side driver using the TUB as a common terminal can be realized on a single chip with lower cost.
However, in the conventional layout design, the high-voltage high-side and low-side devices as well as the two high-voltage devices in the high-voltage level shifter are implemented separately in one chip, and each of them has its own voltage-sustaining region. It is well known that the higher the sustaining voltage is, the wider the voltage-sustaining region is, and thus each high-voltage device needs a larger area for transmitting signals, whereas the current for transmitting signals in the two high-voltage devices in high-voltage level shifter is small. Thus, even the edge terminations of the two devices are round ones, the two devices still need a large area of a chip, because the radii of the device are longer than the length of the voltage-sustaining region.
In addition, if the two devices are individually made in different regions, the interconnection between the high-voltage terminals with regard to the substrate of them must have their own pads, and outer connections is indispensable, which leads increasing of the area of a chip and make the technology more complicated.